A large number of commercial and factory or plant roofs are of a flat roof design wherein the roofing material itself is often of built-up asphalt, and, in more modern systems, of a single ply EPDM elastomeric sheet or membrane. In terms of securing a single ply EPDM membrane to the roof itself, one common design utilized is the mechanical ballast system that uses a layer of stone over the membrane. While the ballast system is least expensive, it has the disadvantage of being quite heavy (about ten pounds per square foot) thus requiring a heavy roof support structure and, in addition, the roof slope cannot exceed 10.degree..
Adhered roof membrane retention system suffer from a cost penalty while mechanical fastening systems generally require a fixation to the roof substrate by metal fasteners with metal or rubberized nailing strips. Additional sealing strips or caps are then required to keep the punctured membrane water tight. Such installations are cumbersome as well as time consuming in addition to violating the integrity of the membrane itself.
Co-pending U.S. application Ser. No. 516,618 to Yang, et al, filed July 25, 1983, and assigned to common assignee, discloses a mechanical fastening system for securing a flexible sheet within a channel member via an insert member wherein the latter is made of flexible resilient material having a central longitudinal flex notch that serves to define two adjacent wing portions and permits a temporary elastic deformation of the insert member into an inverted V-shape for insertion of the insert member, together with adjacent portions of the flexible sheet, into the channel member. In the interest of full disclosure, this application is incorporated herein by reference to the extent necessary to explain this particular mechanical fastening system.
Co-pending U.S. application Ser. No. 524,511 to Dubich, et al, filed Aug. 18, 1983, and assigned to common assignee, discloses a membrane fastener apparatus, including a placing tool assembly that sequentially horizontally deforms the flexible resilient strip into an inverted V-shape; thereafter, grips the apex portion of the inverted V-shaped strip and pushes the strip, together with the abutting portions of the flexible membrane, into the channel member. Subsequently, a pressing tool assembly contacts the apex portion of the inverted V-shaped insert strip to both fully insert the strip into the channel member and thereafter return the strip to approximately its natural shape, so as to frictionally and non-bindingly retain adjacent portions of the membrane within the channel member. To the extent necessary, this application is also incorporated herein by reference in the interest of full disclosure.
Co-pending U.S. application Ser. No. 516,622 to Yang, et al, filed July 25, 1983 and assigned to common assignee, discloses an attachment device for securing flexible sheets within a channel member via an insert member of generally inverted V-shape wherein the latter is made of ductile but rigid material having a central longitudinal portion of reduced rigidity that serves to define two adjacent wing portions and permits the subsequent plastic deformation of the insert member into its installed shape after its insertion, together with adjacent portions of the flexible sheet, into the channel member. Again, in the interest of full disclosure, this application is incorporated herein by reference to the extent necessary to explain this particular attachment device.
In both the previously-noted mechanical fastening system and attachment device, the insert member serves to retain adjacent portions of the flexible membrane within the channel member. Under normal design conditions, these insert members fully perform their function of retaining the flexible membrane within the channel member. It is conceivable, however, that excess force or pressure could possibly cause sufficient deformation of either the channel member or insert member so as to cause the removal of the insert member from the channel member and thereafter permit the removal of the flexible sheet from the channel member.